Research On The Energy-saving Equipments For Fruits And Vegetalbes Expansion Puffing

The low-temperature and high-pressure expansion puffing equipment(LHEE) was taken as the object, the energy-saving research on the expansionpuffing equipments for fruits and vegetables in the food industry was made. TheLHEE in the mature market was analyzed and evaluated, the strengths andweaknesses of which were pointed out. The expansion puffing tank and vacuumtank required by classic LHEE were designed. The energy analysis and exergyanalysis on the whole expansion puffing equipment were made, combining withthe production process in the scope of first and second laws of thermodynamics,what obtained were that the energy loss mainly existed in the process of heatingand cooling equipments. The exergy loss mainly existed in the process of heattransfer, and the amount of exergy loss was huge, cause of that the heatingprocess was from normal temperature to technology high temperature and thecooling process was also from high temperature to normal temperature, whichbrought about large temperature difference, and the bigger the temperaturedifference of heat transfer, the bigger the exergy loss. The removing of water isone of the most important process indicators in the food drying industry, thecondition of water transfer in the whole explosion puffing operating wasanalyzed and calculated, by combining the schematic diagram, the water contentof material in every stage of explosion puffing process was provided. Andaccording to analysis, the disposal method of condensate water which couldinfluence the quality of products was offered, which could supply theoreticalbasis for consummating the process of LHEEThe energy gradient utilization method was researched by combining themain characteristics and existed position of energy loss and exergy loss, whichwas that by utilizing two energy storage equipments the energy recycling duringthe process of heating and cooling the jacket of expansion puffing tank wasrealized. The principle of which was that utilizing two temperature-difference storage tanks preheated the jacket during the heating process and then the hotsource was utilized to heat the jacket directly, and during the process of coolingthe jacket, the temperature-difference storage tanks could precool the jacket andabsorb energy prepared for the next heating process. The temperature and flowparameters of energy gradient utilization were acquired by calculating, the PLCcontrol procedure program was given. By testing and verifying, the energyutilization rate could be promoted theoretically by7.6%, the energy could besaved theoretically by51.63%and29.94%during the heating process and thewhole process, and the whole exergy loss was80%.Different kinds of effective heating methods including superheated steamdrying, microwave drying and far infrared drying were researched during thevacuum drying stage in order to solve the situation that the gas was thin whichled to a bad effect of heat conduction and even made the heat convection ignored.Cause of the own characteristics of far infrared heating and the requirement ofprocess conditions, the far infrared heating was chosen at last. By using thecorresponding laws such as Stephen-Boltzmann law, Lambert law and so on, thedistance between the far infrared heat source was calculated. The reasonablelayout of far infrared heat source to material was provided which made thehomogeneous temperature field maximum optimization on condition ensuringthe efficiency and effectiveness. And the heat-flow density of far infrared heatsource was calculated, which provided the operation reference to actualproduction.The rapid cooling method liquid nitrogen was researched, the neededquantity of liquid nitrogen for once process was calculated, and the airpermeability of puffed apple slices was obtained by experiment, and the optimalvacuuming rate was acquired by combining the air permeability. And thedistribution layout of liquid nitrogen nozzle was roughly provided by combiningthe internal structure of expansion puffing tank, the layout of far infrared quartztube, and the airflow direction of vacuuming.